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This study reports the development, construction, and initial testing of a novel vibrational precipitator (VP), patented at Ohio University in 2016, that uses vibrating metal cables with water running over them to capture particulate matter in an exhaust stream. Unlike traditional electrostatic precipitators relying on electric energy to capture particles, this new system uses the concept of vortex shedding to produce vibrations in vertical cables running perpendicular to an exhaust stream. Collisions between particles in the exhaust stream and these vibrating cables cause the particles to land onto a thin film of flowing water around the cables, which carries the particles downward for collection and removal. Initial tests with air containing particulates of 3 micron average particle size show capture efficiencies up to 54% using U.S. Environmental Protection Agency (EPA) Method 5 to measure the particulate concentrations at the upstream and downstream of a VP comprising 8 cells. These results show that this system, without consuming any electric energy, has a significant potential to be a simple and cost-effective way to treat particle-laden exhaust gases. Implications: In this work, for the first time, a novel precipitator is investigated that captures particles without using any particle charging and (hence) any electricity. The capture mechanism is governed by vibrations of collection electrodes, which are vertical steel cables wetted through continuous flow of water. Without any discharge electrodes, electrode suspension mechanism, and ability of the system to be installed in existing ducts, the novel precipitator becomes a simple chamber housing containing multiple collection electrode cells. The preliminary results show that this new technology can achieve net particulate matter capture efficiency of 54%. This paves a pathway forward for reducing capital and operating cost of air pollution control systems.

This paper presents experimental performance characteristics of fixed-geometry hydrodynamic thrust bearings machined to different helical taper depths. Theoretical analysis based on the Reynold’s equation states that under favorable conditions, these taper depths can produce and maintain load-supporting hydrodynamic pressure yet result in characteristically different oil-film pressure distribution profiles and magnitudes of friction torque. These characteristic performance indicators have not previously been observed experimentally for unidirectional fixed-geometry hydrodynamic thrust bearings with helically tapered pads. An experimental test rig was developed by re-purposing a horizontal milling machine capable of subjecting the test bearings to speeds up to 1,265 rpm and axial loads up to 250 lbf (1,112 N). Under various combinations of constant speed, load, and lubrication supply conditions, the steady-state oil-film pressure distribution across the bearing pad and active friction torque are measured. The effects of variable taper-depth on hydrodynamic pressure distribution and friction torque are compared and discussed.

Tapered-land hydrodynamic thrust bearings require taper depths of approximately 20–100 μm to operate efficiently within the hydrodynamic regime. Machining the tapers in traditionally manufactured bearings increase production time and costs. The thermo-mechanical analysis presented in this work shows that the utilization of composite laminas in place of taper machining may be used to provide taper formation in hydrodynamic bearings by exploiting the thermal expansion produced from frictional heating. Thermal expansion of three different carbon/epoxy composite layups (AS-4/3501-6, IM7/3501-6, T-300/3501-6) was analyzed using ABAQUS/CAE composite module. The analysis shows that the composites provide bidirectional taper depths of 24.25 μm, 23.7 μm, and 22.27 μm while being subjected to in-service film pressures and temperatures.

This research presents a newly developed hydrodynamic test rig for experimental testing of hydrodynamic thrust bearings. In this study, the test rig applies thrust loads up to 500 lbf at rotational speeds up to 6,000 rpm. Three fixed geometry hydrodynamic thrust bearings with eight identical helically tapered thrust pads made of cast aluminum alloy have each been machined such that the depth of their tapered surface at the leading edge is 0.0005″, 0.0015″, and 0.0025″ with all other geometrical features held constant. The test rig includes an oil conditioning system which supplies a constant flow of ISO 32 motor oil to the test bearing at 40°C. An integrated sensor system includes an eddy current sensor to measure the minimum oil film thickness, a friction torque moment arm with load cell to measure power loss, K-type thermocouples to measure bearing temperature, pressure transducers to measure oil film pressure distribution, and load cells to measure the applied thrust force. The test rig also introduces a novel bearing alignment system used to ensure precise alignment of the bearing and runner during operation based on pressure feedback from individual thrust pads. Results obtained from this experiment are used to compare the effect of taper geometry on active performance of the test bearings considered. Trends in performance observed are related to the trends predicted analytically by the Reynolds equation.